<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'El.jsp' starting page</title>
    
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->

  </head>
  
  <body>

	算数运算：
	${40+10 }
	<br/>
	关系运算：
	${(4+3)>=(9+5)}
	<br/>
	逻辑运算：
	${!(4+3==7) }
		
	<br/>
	
	Empty:检查空值，如果该值为空，则输出true<br/>
	<% 
		String key1="";
		String key2=" ";
		String key3=null;
		int[] key4=new int[4];
		int[] key5=new int[0];
		request.setAttribute("key1", key1);
		request.setAttribute("key2", key2);
		request.setAttribute("key3", key3);
		request.setAttribute("key4", key4);
		request.setAttribute("key5", key5);
		
		
	%>
	
	${empty key1 }<!-- true -->
	${empty(key2) }<!-- false -->
	${empty(key3) }<!-- true -->
	${empty(key4) }<!-- false -->
	${empty(key5)}<!-- false -->
	${empty(key6) }<!-- true -->
	
  </body>
</html>
